Photoluminescence up-conversion induced by intersubband absorption in asymmetric coupled quantum wells

Abstract

We report a new mechanism of photoluminescence up-conversion in undoped GaAs-AlGaAs asymmetric coupled quantum wells. Under band-to-band excitation, resonant excitation of the ${\mathit{E}}_{1}$\ensuremath{\rightarrow}${\mathit{E}}_{2}$ intersubband transition is shown to result in a finite nonthermal occupation of the ${\mathit{E}}_{2}$ subband, giving rise to an ${\mathit{E}}_{2}$\ensuremath{\rightarrow}${\mathit{HH}}_{1}$ photoluminescence. The induced luminescence closely follows the polarization selection rules and the spectral dependence of the intersubband absorption. We show that this up-conversion scheme can be used to estimate the intersubband scattering time, which is found to be 2.5\ifmmode\pm\else\textpm\fi{}0.7 ps.